The present invention relates generally to a valve and valve assembly, and more particularly to a normally closed valve for use in intravenous medical applications, where the valve is retained in a housing primarily by way of radial forces created by a press fit between a flange on the valve and an inner peripheral surface of the housing.
Although other configurations and intended uses are contemplated, the preferred embodiment of the present invention is a duckbill valve for use in administering fluid to a patient through a Y-site arrangement where two different fluid lines are combined at the Y-site, and where the duckbill valve permits one of the fluids from a first fluid line to flow in a first direction to the patient, but prevents the other fluid from flowing up the first line in the opposite direction to contaminate the supply of the first fluid.
Typically, Y-site valve arrangements are utilized to combine fluids from two different fluid lines, where one line typically provides a continuous flow of saline or equivalent fluid, and the other line generally provides a flow of a predetermined quantity of medication. The two fluids are combined at the Y-site, and the fluid blend is then administered to the patient intravenously. The leg of the Y-site that is connected to the saline line generally includes a valve that allows the saline to flow towards the patient, but does not allow the saline, or, more importantly, the medication from the other line, to flow in the opposite direction. Such a valve prevents the medication from contaminating the saline supply, which may result in the improper dosage of medication being delivered to the patient.
In prior art arrangements, the valve is generally contained within a two part housing assembly, consisting of an upper housing part and a lower housing part. The two parts of the housing assembly are generally made of plastic, and are welded together. The valve is typically seated on a shoulder that is defined on the lower part of the housing assembly, and the valve is maintained in position by axial forces created from the upper part when the two parts of the housing assembly are welded together.
Several problems may result from the valve being axially compressed within the upper and lower housing parts. First, if the axial forces on the valve are not relatively uniformly distributed around the upper surface of the valve, the valve may not be seated properly within the housing, i.e., the valve may be somewhat inclined within the housing. An inclined valve has an increased probability of failure by either not opening at the desired cracking pressure, or by not closing at the desired back pressure.
Either of these types of failure may occur in a duckbill valve, which includes a pair of resilient lips, in which the lips converge in a normally closed slit-like aperture. Failure of a duckbill valve may occur where the lips inadvertently come into contact with the inner walls of the housing assembly. Such contact may prevent the resilient lips from properly opening or closing at the desired pressures. Due to the small size of the valve assembly and the low pressures involved, there is only a very small range of pressures within which the valve must operate. Thus, the valves are extremely sensitive, and even small inaccuracies resulting from assembly errors or tolerance errors can possibly result in failure.
In addition to the problems associated with contact between the lips and the housing, it is also somewhat difficult to obtain consistent welds between the housing components due to the inclusion of a third component, the valve, which is sandwiched between the two housing components. Inconsistent welds may occur because the spacing between the two housing components is not always uniform due to the valve being interposed between the two housing parts.
Consequently, in response to the these problems, it is one object of the present invention to provide an improved valve assembly design that is less susceptible to failure and leakage than other designs where the valve is retained between two housing components via axial compression.
Another object is to provide a design for an improved valve assembly where it is possible to obtain consistent and reliable welds between the two housing components because the valve is no longer involved in the welding process.
A further object of the present invention is to provide a design for an improved valve assembly where the valves may be consistently properly seated within the housings, without the valves being inclined with respect to the housings, so that this potential source of valve failure is substantially eliminated.
A related object of the present invention is to supply a design for an improved valve assembly where the valves each include a pair of resilient lips that converge to form a normally closed slit-like aperture and where the valves are each seated within a housing in such a manner that the resilient lips are consistently out of contact with the inner peripheries of the housings.
It is yet another object of the present invention to provide an improved valve assembly where the valve is retained within the housing via radial compression.
Still another object of the invention is to supply an improved valve assembly where the valve includes a shoulder and the valve is seated within the housing via radial compression such that an air space is created between the lower surface of the shoulder of the valve and the housing.
Yet another object of the present invention is to provide an improved valve assembly in which the valve is maintained in the housing without relying upon axial compression.